Valve assembly with load holding function

Abstract

Valve assembly (10) with a housing (20) in which a first valve body (40) is slidably received, such that a first valve seat (43) on the housing (20) can be closed with a first sealing surface (44) on the first valve body (40), wherein the housing (20) has a first and a second working chamber (21; 22) which are connected to each other via the first valve seat (43), wherein the first valve body (40) together with the housing (20) defines a first control chamber (11) whose volume decreases continuously when the first valve body (40) is moved away from the first valve seat (43), wherein the housing (20) and the first valve body (40) together define a first throttle (13) whose free cross-sectional area increases continuously when the first valve body is moved away from the first valve seat (43), wherein the first working chamber (21) is connected to a second control chamber (12) via the first throttle (13),wherein the second control chamber (12) is connected to or coincides with the first control chamber (11), characterized in that a second valve body (70), different from the first (40), is slidably received in the housing (20), such that a second valve seat (71) on the housing (20) can be closed with a second sealing surface (72) on the second valve body (70), wherein the second working chamber (22) is connected to the second control chamber (12) via the second valve seat (71) in such a way that a pressure acting from the second working chamber (22) pushes the second valve body (70) away from the second valve seat (71), wherein a pressure acting from the second control chamber (12) pushes the second valve body (70) towards the second valve seat (71), wherein the second working chamber (22) is connected to the second control chamber (12) via a pilot valve (80) and bypassing the second valve seat (71).

Description

The invention relates to a valve assembly according to the preamble of claim 1.U.S. Pat. No. 4,779,836 discloses a valve assembly. The valve assembly comprises a housing in which a first valve body is movably accommodated, so that a first valve seat on the housing can be closed by a first sealing surface on the first valve body. Furthermore, the housing has a first and a second working chamber which are connected via the first valve seat. By displacing the first valve body, the flow resistance can be adjusted which counteracts the pressure fluid flowing from the first to the second working chamber.For adjusting the position of the first valve body, a first control chamber is provided, which is delimited by the first valve body and by the housing in such a way that its volume steadily decreases as the first valve body moves away from the first valve seat. Furthermore, a first throttle is provided, which is bounded by the first valve body and by the housing and whose free cross-sectional area increases steadily as the first valve body moves away from the first valve seat. The second working chamber is connected via the first throttle to a second control chamber, which coincides with the first control chamber in U.S. Pat. No. 4,779,836 A. Furthermore, a control volume flow can be derived from the first control chamber by means of an auxiliary valve. The position of the first valve body is adjusted such that the main volume flow flowing from the first to the second working chamber is approximately proportional to the control volume flow. With the comparatively small control volume flow, a large main volume flow can thus be controlled. The main volume flow is dependent not only on the setting of the auxiliary valve but also on the pressures in the first and in the second working chamber.With the valve assembly according to U.S. Pat. No. 4,779,836 A, both a volume flow which flows from the first to the second working chamber and a volume flow which flows in the opposite direction can be controlled.DE 197 15 020 A1 discloses a hydraulic control arrangement which uses load compensation with a pressure compensator, wherein the pressure compensator regulates the pressure drop at an adjustable orifice of a valve slide to a predefinable value. Such load compensation can be dispensed with with with the valve assembly according to the invention, wherein the volume flow nevertheless depends only slightly on the load pressure.DE 102 24 740 A1 shows a hydraulic control valve device with a flow regulating device, wherein here too a pressure compensator is used which regulates the pressure drop at a diaphragm.The object of the present invention is that a control of the volume flow can take place only with respect to a flow from the first to the second working chamber, wherein the valve assembly automatically, leakage-free closes off a fluid flow flowing in the opposite direction. The valve assembly according to the invention thus assumes the function of a load-holding valve without the construction outlay being increased significantly compared to the known valve assembly.According to the invention, it is proposed that a second valve body different from the first is accommodated in the housing such that it can be displaced, so that a second valve seat on the housing can be closed by a second sealing surface on the second valve body, wherein the second working chamber is connected via the second valve seat to the second control chamber in such a way that a pressure acting from the second working chamber presses the second valve body away from the second valve seat, wherein a pressure acting from the second control chamber presses the second valve body towards the second valve seat, wherein the second working chamber is connected via a pilot valve and, bypassing the second valve seat, to the second control chamber. The pilot valve is preferably designed such that it can selectively shut off or open the connection from the second working chamber to the second control chamber.When the valve assembly flows through from the first working chamber to the second working chamber, the pressure in the first working chamber is greater than in the second working chamber. The pressure in the first or second control chamber is thus also greater than in the second working chamber. The second valve body accordingly closes the second valve seat as long as the pilot valve is closed. As soon as the pilot valve is opened, pressure fluid flows out of the first or second control chamber to the second working chamber. As a result, the pressure in the first or second control chamber falls, so that the second valve seat is opened. Accordingly, the pilot volume flow already mentioned flows from the first or second control chamber to the second working chamber, and the above-described control of the main volume flow takes place.If the pressure in the second working chamber now rises above the pressure in the first working chamber, the second valve body is lifted from the second valve seat independently of the position of the pilot control valve. Pressurized fluid flows from the second working chamber into the first control chamber. As a result, the volume of the first control chamber increases, as a result of which the first sealing surface of the first valve body is pressed against the first valve seat. The connection from the first to the second working space is thus tightly closed. It is thus excluded that pressure fluid flows from the second to the first working chamber.The first and / or the second working space can be used to address a channel in the housing, which channel has an opening on the outer surface of the housing, so that other separate structural units can be connected thereto. However, it can also be an internal connecting channel in an integrated valve unit, which has further hydraulic functional units in addition to the valve assembly according to the invention. The valve assembly is preferably used in conjunction with incompressible pressurized fluid, in particular hydraulic oil.The dependent claims specify advantageous refinements and improvements of the invention.The pilot valve can be designed as a seat valve. This prevents the first valve seat from being opened solely on account of undesired leaks at the pilot valve. The corresponding valve body is preferably designed as an elongated circular cylinder, which has a circular-cone-shaped end surface, which serves as a sealing surface.The first working chamber can be connected to the first throttle via a check valve, which permits only a flow of fluid from the first working chamber to the first throttle, wherein the check valve is designed in the form of a poppet valve. This ensures, even in the case of fluctuating pressures in the first working chamber, that the pressure fluid can flow out of the first or second control chamber exclusively via the second valve body, so that the setting of the pilot control valve alone is decisive for the main volume flow. The design as a seat valve moreover has the effect that no undesired leaks occur in the blocked operating state of the valve assembly.The pilot valve can comprise a magnet coil and a magnet armature, wherein the pilot valve can be actuated by the magnet armature, wherein the magnet coil and the magnet armature are matched to one another such that the position of the magnet armature changes continuously when the current in the magnet coil changes. This makes it possible to continuously adjust the pilot volume flow and thus the main volume flow. It should be noted here that by far the most known solenoid actuators are of the switching type, i.e. the solenoid armature can be moved only in one of the two end positions. The mentioned coordination is preferably effected by a suitable spatial arrangement of a non-magnetic flux interruption region in the pole tube surrounding the armature.The magnet armature can be prestressed by a spring into the blocked position of the pilot control valve. This ensures that, in the event of a failure of the above magnetic control, no undesired movements occur on an actuator connected to the workstations. The connection from the first to the second working space is safely blocked in this case.The first control chamber can be formed separately from the second control chamber, wherein the second control chamber comprises a first annular groove in the housing, which surrounds the first valve body. This ensures that the first throttle always opens into the first annular groove independently of the rotational position of the first valve body in the housing. The first throttle preferably comprises at least one notch in a circumferential surface of the first valve body.The first valve body can abut the housing between the first annular groove and the first control chamber. This prevents the first valve body from tilting in the housing, so that it can no longer be moved. It should be noted here that the inclination to the tilting is primarily of importance to the ratio between the diameter and the sliding-guided length of the first valve body. Furthermore, the second throttle, in particular its control edge, is protected from damage during the assembly of the first valve body in the housing.The first and the second control chamber can be connected to one another exclusively via a second throttle. During a movement of the first valve body, pressure fluid is exchanged between the first and the second control chamber. This fluid flow flows via the second throttle, so that the movement of the first valve body is damped. As a result, the risk of the first valve body being excited to perform an oscillating movement falls. The second throttle can be formed by a closed channel, in particular a bore, in the first valve body or by an open channel, in particular a slot, on the outer circumferential surface of the first valve body. However, a closed channel can also be provided in the housing.The free cross-sectional area at the first valve seat can continuously change with the displacement of the first valve body according to a nonlinear first characteristic curve. The first characteristic curve can run parabolically.An end face of the first valve body adjacent to the first sealing surface can be formed convexly curved at least adjacent to the first sealing surface. As a result, the first characteristic curve can be set.The first valve body can have a plurality of first bores which extend radially with respect to its direction of movement and which are covered or not covered by the housing depending on the position of the first valve body, wherein the first bores are connected in series with the first valve seat. By selecting a suitable arrangement and suitable diameters of the first bores, the first characteristic curve can be set.The first throttle may have a non-zero free cross-sectional area when the first valve seat is closed by the first valve body. This improves the fine controllability of the valve assembly. In particular, only the pilot valve can be used for setting very small main volume flows. The first valve seat remains completely closed in this operating state, i.e. the pressurized fluid flows from the first working chamber via the first throttle into the second control chamber and from there further solely via the pilot valve into the second working chamber.The free cross-sectional area of the first throttle can continuously change with the displacement of the first valve body according to a nonlinear second characteristic curve. A linear second characteristic curve can also be used.It is understood that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention.The invention is explained in more detail below with reference to the attached drawings. It represents: FIG. 1 is a sectional view of a valve assembly according to a first embodiment of the invention; FIG. 2 shows a detail of the view according to FIG. 1 in the region of the check valve; FIG. 3 shows a detail of the view according to FIG. 1 in the region of the second valve body; FIG. 4 is a partial sectional view of a valve assembly according to a second embodiment of the invention in the region of the first valve seat; and FIG. 5 is a partial sectional view of a valve assembly according to a third embodiment of the invention in the region of the first throttle.FIG. 1 shows a sectional view of a valve assembly 10 according to a first embodiment of the invention. The valve assembly 10 comprises a housing 20 which can be composed of a first, a second and a third housing part 23; 24; 25 and a first and a second closure screw 31; 32, wherein said parts are firmly connected to one another. In the first housing part 23, a first valve body 40 is accommodated movably with respect to a direction of movement 15 that is horizontal in FIG. 1. The circumferential surface of the first valve body 40 has a first and a concentric second circular cylindrical region 41; 42, wherein the diameter of the second circular cylindrical region 42 is smaller than that of the first circular cylindrical region 41. Between the first and the second circular cylindrical region 41; 42 a first sealing surface (no. 44 in FIG. 2 ) is arranged, which is formed in the shape of a circular cone. The first sealing surface 44 is assigned a first valve seat (no. 43 in FIG. 2 ), which is closed by the first sealing surface 44 in a leak-free, tight manner in the position shown. The first valve seat 43 contacts the first sealing surface 44 along a line that extends annularly around the first valve body 40.The first and the second circular cylindrical bore 29; 30 in the housing are adapted with very little play to the associated first and second circular cylindrical region 41; 42 of the first valve body 40, so that the first valve body 40 is still easily movable, wherein virtually no pressure fluid can pass through the corresponding gap. Furthermore, the housing has a first and a second annular groove 26; 27 which annularly surround the first valve body 40. A third annular groove 28 is arranged on the left in FIG. 1 next to the first valve body 40.The third annular groove 28, together with a channel connected thereto, forms the first working chamber 21, which is preferably connected at least indirectly to a pressurized fluid source, in particular a hydraulic pump. The second annular groove 27 forms, together with a channel connected thereto, the second working space 22, which is preferably connected at least indirectly to an actuator, for example a hydraulic cylinder. The first annular groove 26 is part of the second control chamber 12, which furthermore comprises a channel which leads to the second valve body 70.The first control chamber 11 is delimited by the housing 20 and by an end face of the first valve body 40. The first locking screw 31, which is screwed into the first housing part 23, is considered to be a component of the housing 20. A third locking screw 65 is screwed into the end face of the first valve body 40, so that the second valve body 40 is closed there in a fluid-tight manner. The single connection of the first control chamber 11 to the outside runs via the second throttle 14 to the second control chamber 12, it being noted here that the first valve body 40 bears between the first and the second control chamber 11; 12 over its entire circumference against the first circular-cylindrical bore 29.A spring 48, which is preferably designed as a helical spring, is received in the first control chamber 11 under prestress, so that the first valve body 40 is pressed with its first sealing surface against the first valve seat. As soon as the first valve body 40 is lifted from the first valve seat by the application of pressure from the first working chamber 21, the volume of the first control chamber 11 decreases, wherein the corresponding incompressible pressure fluid flows out through the second throttle 14 to the second control chamber 12. From there it cannot flow off via the first throttle 13, because the corresponding connection is blocked by the check valve 60. Further details in this respect are explained with reference to FIG. 2.In the third housing part 25, which is fixedly installed in the second housing part 24, the second valve seat (no. 71 in FIG. 3 ) is arranged, via which the second working chamber 22 is connected to the second control chamber 12. A second valve body 70 is associated with the second valve seat, the details of which are described in more detail with reference to FIG. 3. The second valve seat can be closed with the second valve body 70 without leakage.Furthermore, a pilot valve 80 is provided, which can open the communication between the second working chamber 22 and the second control chamber 12 by bypassing the second valve seat. Pilot valve 80 includes a fourth valve body 81 in the form of a valve needle, which is part of a poppet valve. The fourth valve body 81 is motion-coupled to a magnet armature 84 which is accommodated in a pole tube 87 sealed in a fluid-tight manner so as to be displaceable in the direction of movement 15. The pole tube 87 is largely made of a magnetizable material such as steel. Only in the flux interruption region 88 is the pole tube 87 made of a nonmagnetizable material such as copper. Alternatively, magnetizable material having a much smaller wall thickness compared to the rest of the pole tube can also be provided in the flux interruption region 88. The length and the arrangement of the flux interruption region 88 is selected such that the armature moves steadily with increasing current intensity in the magnet coil 85, wherein ideally a linear relationship between current intensity and displacement of the magnet armature 84 is sought. The magnet armature 84 is pressed by a prestressed spring 86 in the direction of the second valve seat 71, with the result that the spring force must be overcome by the magnetic forces.Furthermore, a second locking screw 32 is screwed into the first housing part 23, which is likewise regarded as a component of the housing 20. The second locking screw 32 seals the first working space 21. The third housing part 25 is firmly connected, in particular screwed, to the pole tube 87. The pole tube 87 is in turn firmly connected, in particular screwed, to the second housing part 24, wherein the third housing part 25, the pole tube 87 and the magnet coil 85 form a separate structural unit, which is also referred to as a screw-in valve.FIG. 2 shows a detail of the view according to FIG. 1 in the region of the nonreturn valve 60; a longitudinal bore 45 which has a plurality of steps passes through the first valve body 40 over its entire length. On the right-hand side in FIG. 2, the longitudinal bore 45 is tightly closed by the third locking screw (no. 65 in FIG. 1 ). The longitudinal bore 45 comprises a third valve seat 63 in which a circular cylindrical surface and a circular conical surface intersect. In the first valve body 40, a third valve body 61 is accommodated such that it can be displaced with respect to the direction of movement 15. The third valve body 61 is part of a non-return valve 60 designed as a seat valve, and it has a circular-conical third sealing surface 64, which in the position shown bears against the third valve seat 63 along an annular line. A spring 66, in particular a helical spring, is installed under prestress between the third valve body 61 and the third locking screw 65, so that the third valve body 61 is pressed against the third valve seat 63. The corresponding cavity is connected to the first throttle 13 via the transverse bore 62, so that the pressure acting from the first throttle 13 via the second radial bores 47 presses the check valve 60 into the closed position. Pressure acting from the first working chamber (no. 21 in FIG. 1 ) on the third valve body 61 lifts the latter off from the third valve seat 63 so that the check valve 60 allows a fluid flow from the first working chamber to the first throttle 13 and therefore to the second control chamber, but not a fluid flow in the opposite direction.At this point, reference should be made to the gap, denoted by the reference numeral 67, between the first circular-cylindrical region 41 of the first valve body 40 and the first circular-cylindrical bore 29 in the housing 20, which is situated between the second annular groove 27 and the second radial bores 47. This gap 67 allows unavoidable leakage currents to flow. This leakage flow is, however, tightly shut off by the check valve 60 as far as it is directed from the second to the first working chamber. A leakage flow in the opposite direction, however, is not sealed off, wherein it generally does not interfere, since a very much larger fluid flow flows in parallel via the first valve seat 43 from the first to the second working chamber.On the left-hand side of the first valve body 40 in FIG. 2, a plurality of first bores 46; 46a running in the radial direction are provided, with some bores 46a having a larger diameter than the other bores 46. When the first valve body 40 is moved away from the first valve seat 43, the first bores 46; 46a come into the region of the control edge 34, a more or less large part of its cross-sectional area being released. By the arrangement of the first bores 46; 46a, it is possible to adjust how the free cross-sectional area at the first valve seat 43 changes with the movement path of the first valve body 40. Preferably, a non-linear first characteristic curve is sought in this respect. In order to pass from the first working chamber 21 to the second working chamber 22, the pressure fluid must first flow via the first radial bores 46; 46a and then through the first valve seat 43. In this respect, a series connection is thus present.FIG. 3 shows a detail of the view according to FIG. 1 in the region of the second valve body 70. the second valve body 70 has a third circular cylindrical region 74, with which it is guided in an adapted bore in the third housing part 25 so as to be movable in a sliding manner in the direction of movement 15. In the third circular cylindrical region 74, the second valve body 70 is provided with a plurality of circumferential grooves 76, which prevent the second valve body 70 from adhering firmly to the third housing part 25 due to adhesion forces. The fourth circular cylindrical region 75 abuts an adapted bore in the third housing part 25 which ends at a control edge 77. In the fourth circular cylindrical region 75, a plurality of fine control notches 78 are provided, which together with the control edge 77 each delimit apertures, the free cross-sectional area of which changes with a displacement of the second valve body. The aforementioned diaphragms are connected in series with a second valve seat 71 whose associated second sealing surface 72 is arranged between the third and fourth circular cylindrical regions 74; 75 on the second valve body 70. The second sealing surface 72 is circular cone-shaped, contacting the second valve seat 71 along an annularly extending line in the position shown. Reference is also made to the transverse bores 33 in the third housing part 25, which produce a connection between the first annular groove (no. 26 in FIG. 1 ) and the second valve seat 71. The pressure in the second working chamber 22 is applied to the end face of the second valve body assigned to the fourth circular cylindrical region 75, so that this pressure can lift the second valve body 70 off the second valve seat 71.A fourth valve seat 82 is provided in the interior of the second valve body 70, said fourth valve seat being formed by a thin bore in the second valve body 70. In the position shown, a fourth sealing surface 83 of a fourth valve body 81 abuts the fourth valve seat 82. The fourth valve seat 82 and the fourth valve body 81 are part of the pilot control valve 80 already mentioned. The fourth valve body 81 is designed in the manner of a valve needle, i.e. it has the shape of an elongated circular cylinder, wherein the fourth sealing surface 83 is designed in the shape of a circular cone tapering to a point. Reference is also made to the transverse bore 73 in the second valve body 70, which establishes a connection between the second control chamber 12 and the fourth valve seat 82 via the transverse bore 33.It should also be noted that the pilot valve 80 is accommodated within the second valve body 70 solely for reasons of saving installation space. It could just as well be arranged at another location in the housing 20. It is only decisive that the pilot valve 80 can establish or close a connection between the second control chamber 12 and the second working chamber 22 parallel to the second valve seat 71.FIG. 4 shows a partial sectional view of a valve assembly 10 bin accordance with a second embodiment of the invention in the region of the first valve seat 43. the second embodiment corresponds with the first embodiment in accordance with FIGS. 1 to 3 except for the differences described below, so that reference is made in this respect to the above explanations. In FIG. 4, corresponding parts are identified by the same reference numerals.FIG. 4 shows the first valve body 40 in a position in which its first sealing surface 44 is lifted from the first valve seat 43.Instead of the first radial bores (no. 46; 46 ain FIG. 2 ), a convexly curved region 50 is provided on the end face 49 of the first valve body 40 adjacent to the first sealing face 44. The free cross-sectional area in the region of the first valve seat 43 is determined by the distance between the control edge 34 and the convexly curved region 50. This distance preferably changes according to a first characteristic curve which is nonlinear and, for example, parabolic.FIG. 5 shows a partial sectional view of a valve assembly 10 cin accordance with a third embodiment of the invention in the region of the first throttle 13, the third embodiment corresponding to the first embodiment in accordance with FIGS. 1 to 3 except for the differences described below, so that reference is made in this respect to the above explanations. In FIG. 5, corresponding parts are identified by the same reference numerals.The first throttle 13 is designed as notches in the first valve body 40, as in FIG. 2. However, the depth thereof no longer changes linearly but rather non-linearly over the length of the first valve body 40 In this case, a progressive course of the free cross-sectional area of the first throttle 13 over the displacement path of the first valve body 40 is provided.FIG. 5 shows the first valve body 40 in a position in which the first valve seat is closed. It can be seen that the first throttle 13 already has a free cross-sectional area in this position. This is also the case in the first embodiment according to FIG. 2.List of reference characters10 Valve assembly (first embodiment) 10 aValve assembly (second embodiment) 10 bValve assembly (third embodiment) 11First control chamber 12Second control chamber 13First throttle 14Second throttle 15 Direction of movement 20 Housing 21First working chamber 22Second working chamber 23First housing part 24Second housing part 25Third housing part 26First annular groove 27Second annular groove 28Third annular groove 29First circular cylindrical bore 30Second circular cylindrical bore 31First screw plug 32Second screw plug 33 Querbohrung bore 34 Control edge 40First valve body 41First circular cylindrical region 42Second circular cylindrical region 43First valve seat 44First sealing surface 45 Längsbohrung bore 46, 46 afirst radial bore 47 second radial bore 48 spring 49 end face 50 convexly curved region 60 nonreturn valve 61 third valve body 62 transverse bore in valve body 63 third valve seat 64 third sealing surface 65 third closing screw 66 spring 67 gap with leakage 70 second valve body 71 second valve seat 72 second sealing surface 73 transverse bore 74 third circular cylindrical region 75 fourth circular cylindrical region 76 encircling groove 77 control edge 78 fine control notch 80 pilot valve 81 fourth valve body 82 fourth valve seat 83 fourth sealing surface 84 magnet armature 85 magnet coil 86 spring 87 pole tube 88 flow interruption region

Claims

Valve assembly (10) having a housing (20) in which a first valve body (40) is accommodated displaceably, such that a first valve seat (43) on the housing (20) can be closed by a first sealing surface (44) on the first valve body (40), wherein the housing (20) has a first and a second working chamber (21; 22) which are connected to one another via the first valve seat (43), wherein the first valve body (40) together with the housing (20) delimits a first control chamber (11), the volume of which decreases continuously on displacement of the first valve body (40) away from the first valve seat (43), wherein the housing (20) and the first valve body (40) together delimit a first throttle (13), the free cross-sectional area of which increases continuously on displacement of the first valve body away from the first valve seat (43), wherein the first working chamber (21) is connected via the first throttle (13) to a second control chamber (12), wherein the second control chamber (12) is connected to the first control chamber (11) or coincides with the latter, characterized in that a second valve body (70) different from the first (40) is accommodated displaceably in the housing (20), such that a second valve seat (71) on the housing (20) can be closed by a second sealing surface (72) on the second valve body (70), wherein the second working chamber (22) is connected via the second valve seat (71) to the second control chamber (12) in such a way that a pressure acting from the second working chamber (22) presses the second valve body (70) away from the second valve seat (71), wherein a pressure acting from the second control chamber (12) presses the second valve body (70) towards the second valve seat (71), wherein the second working chamber (22) is connected to the second control chamber (12) via a pilot valve (80) and bypassing the second valve seat (71).Valve assembly according to Claim 1, characterized in that the pilot valve (80) is designed as a seat valve.Valve assembly according to one of the preceding claims, characterized in that the first working chamber (21) is connected to the first throttle (13) via a check valve (60), which permits only a flow of fluid from the first working chamber (21) towards the first throttle (13), wherein the check valve (60) is designed in the form of a seat valve.Valve assembly according to one of the preceding claims, characterized in that the pilot valve (80) comprises a magnet coil (85) and a magnet armature (84), wherein the pilot valve (80) can be actuated by the magnet armature (84), wherein the magnet coil (85) and the magnet armature (84) are matched to one another such that the position of the magnet armature (84) changes continuously when the current in the magnet coil (85) changes.Valve assembly according to Claim 4, characterized in that the magnet armature (84) is prestressed by a spring (86) into the blocked position of the pilot control valve (80).Valve assembly according to one of the preceding claims, characterized in that the first control chamber (11) is formed separately from the second control chamber (12), wherein the second control chamber (12) comprises a first annular groove (26) in the housing (20), which surrounds the first valve body (40).Valve assembly according to Claim 6, characterized in that the first valve body (40) bears against the housing (20) between the first annular groove (26) and the first control space (11).Valve assembly according to Claim 6 or 7, characterized in that the first and the second control chamber (11; 12) are connected to one another exclusively via a second throttle (14).Valve assembly according to one of the preceding claims, characterized in that the free cross-sectional area at the first valve seat (43) changes continuously with the displacement of the first valve body (40) according to a nonlinear first characteristic curve.Valve assembly according to Claim 9, characterized in that an end face of the first valve body (40) which is adjacent to the first sealing surface (44) is formed in a convexly curved manner (50) at least adjacent to the first sealing surface (44).Valve assembly according to Claim 9, characterized in that the first valve body (40) has a plurality of first bores (46; 46a) which run radially with respect to its direction of movement and which are covered or not covered by the housing (20) depending on the position of the first valve body (40), the first bores (46) being connected in series with the first valve seat (43).Valve assembly according to one of the preceding claims, characterized in that the first throttle (13) has a free cross-sectional area which is different from zero when the first valve seat (43) is closed by the first valve body (40).Valve assembly according to one of the preceding claims, characterized in that the free cross-sectional area of the first throttle (13) changes continuously with the displacement of the first valve body (40) according to a nonlinear second characteristic curve.

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